What do the following two equations represent? $-5x-5y = -5$ $20x-20y = 2$
Solution: Putting the first equation in $y = mx + b$ form gives: $-5x-5y = -5$ $-5y = 5x-5$ $y = -1x + 1$ Putting the second equation in $y = mx + b$ form gives: $20x-20y = 2$ $-20y = -20x+2$ $y = 1x - \dfrac{1}{10}$ The slopes are negative inverses of each other, so the lines are perpendicular.